Why do astronomers rarely use miles or kilometers when using distances in space?

Question

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Answer 1

First of all, astronomers rarely use miles because that's the English system of measurement which is only used by the U.S and a small handful of other countries. So Astronomers stick to the international SI measurements which would be meters, liters, grams,ect. But astronomers do rarely use kilometers, so instead they use millimeters because it would be more exact. Astronomers also use astronomical units (AU) which is:
1AU=93 million miles which is of course the distance of the sun from earth. Or they would also use light years which is the distance that light travels in a year. For example, if a star is 60 light years from us, it would take light from that star 60 years to reach earth.

Answer 2

They usually use Astronomical Units which is the distance of the Sun from the Earth...93 million miles, for certain measurements. Usually distances to stars and galaxies and other extra-solar items are measured in light years. A light is the distance that light travels in one year at 183,000 miles/second. If they use miles and kilometers, heck, we have to have tonnes of books and have to cut down a lot more trees. It is also very cumbersome when it comes to calculations.

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Answer 3

First-- no sciences use English measurements, so they wouldn't ever measure anything in miles. They wil always measure things in metric terms.

secondly-- the distances involved in astronomical observations as so amazingly large that kilometers are microscopically small by comparison.

In astronomy disatances are measured in a term called a "light-year". The name sounds like a measurement of time, but in fact, it stands for the distance that light will travel in one year.

Since light travells thousands of kilometers in one second of time, the amount of distance it covers in one year is staggering.

Even larger distances are measure in "parsecs" which is greater than 3 light years, or in "astronomical units" which is a smaller distance equal to the average distance from theEarth to the sun...

Answer 4

they are small when talking about space. It is easer to say the earth is 1 AU from the sun then saying 93,000,000 miles. It also takes less space when you Use Astronomical Units (AU) Or light Years.

Answer 5

Because the distances are too great. It's a lot easier to work with a distance of 1 light year than it is to work with a distance of 9,000,000,000,000 Km

Answer 6

its a question of scale. its why you don't give your hight in millimeters. or your weight in grams or ounces. the measured velocity of light makes a handy scale of very long distances measured in time and speed. thats why a light year is a distance. the distance light travels in 1 year. and as time can be graduated so can your distances. Light seconds, minutes, ect.

Answer 7

Here's a hint:

The distance to the nearest star, after the sun, is about 40,000,000,000,000 kilometres. The distance to the nearest large spiral galaxy is about 250,000,000,000,000,000,000 kilometres.

Get the message?

Answer 8

Because they are too small a unit of measurement for distances in space.

Answer 9

It would be too damn far to express it as miles. It would almost be meanlingess.

Aircraft moves quite a bit faster in space as well - in my opinion it's best to express that in meters/second.

But who cares.

Answer 10

Would you use drops to describe the amount of water in the ocean? Of course not...it would just be silly.